1. Field of the Invention
The invention relates to an ink jet recording apparatus and a recording method and, more particularly, to an ink jet recording apparatus and a recording method for recording by performing a serial scan.
2. Related Background Art
The ink jet recording apparatus has advantages such that a mechanism is simple, it can be easily constructed in a compact size, a color image can be easily formed, and the like, so that it has rapidly been spread in recent years. Although an image formed by such an apparatus is extremely stable for a fluctuation in humidity, there is a problem such that an image density easily fluctuates in the case where the temperature fluctuates. This is because a viscosity of ink changes depending on the temperature, so that an ink ejection amount changes. For example, when the temperature rises, the viscosity of ink decreases, so that the ejection amount increases. When the temperature decreases, the viscosity of ink increases, so that the ejection amount decreases on the contrary.
Among the ink jet recording apparatuses, an apparatus of what is called a bubble jet system in which an electrothermal transducer is heated, the ink is boiled and the ink is ejected out by its pressure, has advantages such that multi-nozzles can be easily formed, a high density can be easily realized and the like. The above system, however, also has a problem such that a density fluctuation is large because of an increase in temperature due to a heat generation of the electrothermal transducer. After the printing is started, the temperature of head gradually rises. Therefore, as the printing operation is continuously executed, the image density increases rather than that just after the start of the printing. After the printing operation was stopped, the density again decreases.
As a method of suppressing a density fluctuation due to an increase in head temperature in the bubble jet system, there is a method of increasing the head temperature by heating the electrothermal transducer by a pulse or voltage having such a width or level as not to eject out the ink. By executing such a heating process before the printing, the image density just after the printing rises and a difference between such a density and the image density when the printing is continued is reduced.
On the other hand, among image recording apparatuses in which a bubble jet head is serially scanned and an image is recorded, there is known an apparatus in which output images are combined and an image of a large area is formed. FIG. 3 shows a state in which a part of a capital letter xe2x80x9cAxe2x80x9d is printed to each of four papers of the Al size by such a recording apparatus and those four papers are combined. In the diagram, xe2x80x9cAxe2x80x9d is drawn as a voided image on a blue background. A mode to obtain an image of a large area by combining a plurality of papers is hereinafter referred to as a xe2x80x9ccontinuous magnify-record modexe2x80x9d. In the diagram, a P direction indicates a main scanning direction of the recording head and an fxe2x80x2 direction indicates a subscanning direction of the recording head.
Among the output images (1) to (4), an image density at a start point of the scan in the P direction is low. A temperature rises in association with the printing operation and the image density also rises and is highest at an end point of the scan. When the printing of one scan is finished, the head doesn""t perform the printing operation and is returned in the direction opposite to the P direction. At this time, the head temperature decreases and the image density is again reduced at the start point of the next scan. Therefore, a difference of the image densities occurs in the end point portion of the scan of (1) and the start point portion of the scan of (2). In dependence on an original, an optical density difference of 0.2 or more occurs.
Further, since the start and end points of the scan are finally located at neighboring positions, a small image density difference becomes very conspicuous. Actually, even when the density difference between (1) xe2x88x92S and (1) xe2x88x92E is equal to about 0.2, it is inconspicuous so long as only one paper of (1) is seen. However, in the neighboring portions of (1) xe2x88x92E and (2) xe2x88x92S, even when there is a density difference of 0.1, it is visually very conspicuous.
Therefore, in order to make the image density difference visually inconspicuous in the continuous magnify-record mode, it is insufficient to merely give a pulse of a duration such as not to eject the ink just before the start of the printing. Particularly, in the case where a scan length in the P direction is set to a large value in order to obtain an image of a large area, the head temperature in one scan largely increases, so that the above problem becomes remarkable.
To prevent such a problem, a method whereby not only a pulse for heating the head is given just before the start of the printing but also such a pulse is positively given is considered. However, when the head is excessively heated, there is a case where the life of head is reduced. Although there are various structures of the print head, generally, a nozzle and a top plate or a nozzle and a board of the heater are adhered. In such a case, when a heat pulse is excessively applied, a problem such that a temperature of adhesive agent too rises and the adhesive agent is peeled off occurs.
It is an object of the invention to provide ink jet recording apparatus and recording method which can suppress a fluctuation of an image density due to a temperature fluctuation, for example, a fluctuation of an image density at the start of the recording and the end of the recording.
Another object of the invention is to provide ink jet recording apparatus and method which can minimize a reduction of life of a head.
According to one aspect of the present invention, the above objects are accomplished by an ink jet recording apparatus for recording an image by using a recording head which ejects an ink by a heat generation of an electrothermal transducer, wherein the apparatus comprises: supplying means for supplying a heating signal under conditions such as not to eject the ink to the electrothermal transducer; selecting means for selecting conditions to supply the heating signal; and control means for controlling the supplying means in accordance with the result of the selection of the conditions of the selecting means.
According to another aspect of the invention, the above objects are also accomplished by an ink jet recording apparatus in which a recording head that is constructed by arranging a plurality of ejecting portions each for ejecting an ink by a heat generation of an electrothermal transducer is repetitively scanned in the direction different from the arranging direction of the ejecting portions, thereby recording an image, wherein the apparatus comprises: supplying means for supplying a heating signal under conditions such as not to eject the ink to the electrothermal transducer; selecting means for selecting conditions to supply the heating signal; correcting means for correcting an amount of ink that is ejected to a boundary portion of the image to be recorded by the scan; and control means for controlling the supplying means in accordance with the result of the selection of the conditions of the selecting means and for controlling a correction amount by the correcting means in the scan.
According to still another aspect of the invention, the above objects are accomplished by an ink jet recording method of recording an image by using a recording head to eject an ink by a heat generation of an electrothermal transducer, wherein the method comprises: a setting step of setting conditions to supply a heating signal under conditions such as not to eject the ink to the electrothermal transducer; a heating signal supplying step of supplying the heating signal to the electrothermal transducer in accordance with the set conditions when the image recording is not executed; and an ejecting signal supplying step of supplying an ejecting signal under conditions such as to eject the ink to the electrothermal transducer when the image is recorded.
According to further another aspect of the invention, the above objects are accomplished by an ink jet recording method in which a recording head which is constructed by arranging a plurality of ejecting portions each for ejecting an ink by a heat generation of an electrothermal transducer is repetitively scanned in the direction different from the arranging direction of the ejecting portions, thereby recording an image, wherein the method comprises: a setting step of setting conditions to supply a heating signal under conditions such as not to eject the ink to the electrothermal transducer; a correcting step of correcting an amount of ink that is ejected to a boundary portion of the image to be recorded by the scan on the basis of a correction amount according to the set conditions; a heating signal supplying step of supplying the heating signal to the electrothermal transducer in accordance with the set conditions; and an ejecting signal supplying step of supplying an ejecting signal under conditions to eject the ink to the electrothermal transducer when the image is recorded.
According to the above construction, since the heating signal can be supplied in accordance with the condition to supply the heating signal, the reduction of the life of the head can be minimized and a uniformity of the density can be sufficiently assured as necessary.
FIG. 1 is a block diagram of an embodiment 1 of the invention;
FIG. 2 is a schematic perspective view of a printer which is used in the embodiment of the invention;
FIG. 3 is an explanatory diagram of a copy in a continuous magnify-record mode;
FIG. 4 is a schematic diagram of a printing head which is used in the embodiment of the invention;
FIGS. 5A to 5C are timing charts each showing a sequence in a normal mode in the invention;
FIGS. 6A to 6C are diagrams showing pulse waveforms which are used in the invention;
FIGS. 7A to 7D are timing charts showing a sequence in the continuous magnify-record mode or density fluctuation prevent mode in the invention;
FIG. 8 is a flowchart showing the operation in an embodiment 4;
FIG. 9 is a graph showing the relation between the pulse width of a non-ejection pulse and its optimum applying time in the invention;
FIG. 10 is a block diagram of an embodiment 2;
FIG. 11 is a block diagram of an embodiment 4;
FIGS. 12A and 12B are explanatory diagrams of a boundary blur;
FIG. 13 is a graph showing a correction table of a boundary image signal;
FIG. 14 is a graph showing a table indicating a correspondence relation between T in the embodiment 4 and the correction table;
FIG. 15 is a flowchart showing the operation in the embodiment 4;
FIG. 16 is a diagram showing a table indicating the correspondence relation between T in an embodiment 7 and the correction table; and
FIGS. 17A to 17D are diagrams showing other correction tables of a boundary image signal.